The UC1842/3/4/5 family of control devices provides the necessary features to implement off-line or dc-to-dc fixed frequency current mode control schemes with a minimal external parts count

UC2845

Manufacturer Part NumberUC2845
DescriptionThe UC1842/3/4/5 family of control devices provides the necessary features to implement off-line or dc-to-dc fixed frequency current mode control schemes with a minimal external parts count
ManufacturerTexas Instruments
UC2845 datasheet
 


Specifications of UC2845

TopologyBoost, Flyback, ForwardControl MethodCurrent
Duty Cycle(max)(%)50Frequency(max)(khz)450
Uvlo Thresholds On/off(v)8.4/7.6Pin/package14SOIC, 8PDIP, 8SOIC
Vin(min)(v)7.6Vin(max)(v)30
Regulated Outputs(#)1Operating Temperature Range(c)-40 to 85
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UC1842/3/4/5
UC2842/3/4/5
UC3842/3/4/5
SLUS223C – APRIL 1997 – REVISED JUNE 2007
ELECTRICAL CHARACTERISTICS (continued)
Unless otherwise stated, these specifications apply for –55 C
UC284X; 0 C
T
70 C for the 384X; V
A
PARAMETER
ERROR AMP SECTION
Input Voltage
V
= 2.5 V
PIN 1
Input Bias Current
A
2
V
VOL
O
Unity Gain Bandwidth
T
= 25 C
J
PSRR
12
V
CC
Output Sink Current
V
= 2.7 V, V
PIN 2
Output Source Current
V
= 2.3 V, V
PIN 2
V
High
V
= 2.3 V, R
OUT
PIN 2
V
Low
V
= 2.7 V, R
OUT
PIN 2
CURRENT SENSE SECTION
(6) (7)
Gain
See
Maximum Input Signal
V
= 5 V
PIN 1
PSRR
12
V
CC
Input Bias Current
Delay to Output
V
= 0 V to 2 V
PIN 3
OUTPUT SECTION
I
= 20 mA
SINK
Output Low Level
I
= 200 mA
SINK
I
SOURCE
Output High Level
I
SOURCE
Rise Time
T
= 25°C, C
J
Fall Time
T
= 25 C, C
J
UNDER-VOLTAGE LOCKOUT SECTION
X842/4
Start Threshold
X843/5
X842/4
Min. Operating Voltage After
Turn On
X843/5
PWM SECTION
X842/3
Maximum Duty Cycle
X844/5
Minimum Duty Cycle
TOTAL STANDBY CURRENT
Start-Up Current
Operating Supply Current
V
= V
PIN 2
V
Zener Voltager
I
= 25 mA
CC
CC
(5) These parameters, although specified, are not 100% tested in production.
(6) Parameter measured at trip point of latch with V
A + DVPIN 1
, 0 v VPIN 3 v 0.8 V
DVPIN 3
(7) Gain defined as:
4
T
125 C for the UC184X; –40 C
A
= 15 V; R
= 10 k ; C
= 3.3 nF, T
CC
T
T
UC1842/3/4/5
UC2842/3/4/5
TEST CONDITIONS
MIN
2.45
4 V
65
(5)
0.7
25 V
60
= 1.1 V
2
PIN 1
= 5 V
–0.5
PIN 1
= 15 k
to ground
5
L
= 15 k
to Pin 8
L
2.85
(6)
0.9
(5) (6)
25 V
(5)
= 20 mA
13
= 200 mA
12
(5)
= 1 nF
L
(5)
= 1nF
L
15
7.8
9
7.0
95%
46%
= 0 V
PIN 3
30
= 0.
PIN 2
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T
85 C for the
A
= T
.
A
J
UC3842/3/4/5
TYP
MAX
MIN
TYP
MAX
2.50
2.55
2.42
2.50
2.58
–0.3
–1
–0.3
–2
90
65
90
1
0.7
1
70
60
70
6
2
6
–0.8
–0.5
–0.8
6
5
6
0.7
1.1
0.7
1.1
3
3.15
2.85
3
3.15
1
1.1
0.9
1
1.1
70
70
–2
–10
–2
–10
150
300
150
300
0.1
0.4
0.1
0.4
1.5
2.2
1.5
2.2
13.5
13
13.5
13.5
12
13.5
50
150
50
150
50
150
50
150
16
17
14.5
16
17.5
8.4
9.0
7.8
8.4
9.0
10
11
8.5
10
11.5
7.6
8.2
7.0
7.6
8.2
97%
100%
95%
97%
100%
48%
50%
47%
48%
50%
0%
0%
0.5
1
0.5
1
11
17
11
17
34
30
34
UNIT
V
A
dB
MHz
dB
mA
V
V/V
V
dB
A
ns
V
ns
V
mA
V